I posted in the other thread - probably these should be merged - about my method and a "tweak"
First! I recommend that you order the starter cultures from
Cheeselinkswhich I know will guarantee you a good result. Others who posted on the other thread have tried them and had good results.
There is no guarantee that commercial yogurt will work every time because there are a number of variables over which you have no control. For instance, somewhere between manufacturer and end seller, the yogurt may have been frozen, which makes the culture much less active and unlikely to produce a good result. - when people note that they have a thin or "stringy" result, this can be the reason and also the way you treat the milk, i.e., not heating it to the correct temp, can do the same.
So here is the things you have to keep in mind.
The "trick" to yogurt with good consistency (the gluey and stringy stuff means some organism that is not compatible with the casein in the milk has contaminated the culture) is first heating the milk to the temp where the protein strands are able to relax and this is
82° C.
Then cooling the milk to 45° C and then adding the culture and then maintaining the mile at a fairly constant temperature above 25° C for a minimum of 8 hours - I know some recipes specify shorter times but in my experience the consistency is not as good and I usually extend it to 12 hours, which for me produces a better flavor.
If you are having difficulty using store-bought yogurt, which has to be "pure" with absolutely no additives, no preservatives, do try the yogurt cultures from cheeselinks and I am sure you will be much happier.
You can save some of the finished yogurt to make more but it does have to be re-started after about four batches.
I buy my cultures here in the US from the New England Cheesemaking company and get perfect results every time. I do make repeat batches, using about 1/4 cup of the yogurt, mixed with some of the whey, which I save, but start with a new culture after three batches (2 liters in a batch).
The "TWEAK"
There are ways to speed up the process which are not all that difficult.
I heat milk (2 liters) in the microwave. I have a 2 1/2 liter measuring pitcher - not Pyrex but a similar type of glass.
I take the milk out of the fridge and let it stand at room temp for 2-3 hours so it is not ice cold. I pour it into the glass vessel and microwave it (my microwave is 1000 watts) for 12 minutes which brings it close to the desired temp and then I stir it with a whisk to lift off the "skin" on top, check the temp as I stir with the probe and microwave an additional one or two minutes until it has reached about 185° F. or 85° C.
(You must stir it prior to checking the temp because all liquids heat more rapidly at the upper portion of the mass when there is as sufficient volume and temps can vary by twenty degrees from top to bottom.)
There are various ways to rapidly cool the milk.
Place the container into a larger bowl and fill it with cold water then add ice to the water.
For larger volumes as when I prepare a gallon, I use a narrow plastic cylinder filled with ice that I set down into the milk but for smaller amounts, you can use a couple of large stainless steel spoons that you have placed in the freezer to chill some hours earlier.
Chilling it from both the outside and inside can really cool it within a few minutes.
You have to check the temp often.
The temperature range that is best for adding the yogurt culture (according to the California milk board) is no cooler than 40° C. and no warmer than 46° C. (105 to 115 F.)
Being a little cooler is okay but these are optimum temps to guarantee the best results.
Using purchased cultures instead of commercial yogurt:
How it works is that you save back a small amount of the first batch to make the second batch - also save some of whey and mix it with the solids - and you can do this two or three more times, depending on how long you have held it.
I make a 1/2 gallon (2 liter) batch every three or four days and I always take two or three tablespoons immediately after the batch has finished incubating and put it in a tightly sealed glass container (sterilize it) in the coldest part of the fridge - I add an equal amount of whey when it appears.
I use this starter for the next batch, and so on.
I do it this way so it won't be contaminated by opening and closing the bigger container and introducing spoons, etc., into it.
I also get a Bulgarian culture which is lots more tangy - and somewhat more expensive - from the vendor here in the US and I have kept that culture going for ten repeat batches because it is a very vigorous culture. After the tenth batch the results were not as firm and I started over with a new culture.
The thing is to try it and see how many batches you can get from a single starter.
